1. Field of Invention
The present invention relates an improvement of an orthodontic device in the orthodontic treatment, specifically, to an orthodontic device, which is welded to a band, such as a buccal tube, a lingual sheath, a lingual tube and the like.
2. Description of the Related Art
For orthodontic treatment, brackets retaining an arch wire are fixed on the surfaces of the patient's teeth and the elastic recovery of the arch wire is applied to the teeth via the bracket. The bracket is used with a buccal tube which is fitted over the molars of the patient with the aid of a band and its principal purpose is to retain the ends of the arch wire. As shown in FIGS. 3A and 3B, the buccal tube has a broad weld flange 12. A rectangular tube body 11 and a hook 13 are brazed to the top surface of the broad weld flange 12. The tube body 11 has a through-hole 11a through which an end of the arch wire is detachably passed in a mesiodistal direction. The hook 13 is used to engage an elastic ring or a ligature wire.
With this construction, the buccal tube has the advantage that it can be readily welded in position to the band by virtue of the broad weld flange 12. On the other hand, in order to make the buccal tube, separate components have to be assembled by brazing and this not only lowers the efficiency of construction but also causes the disadvantage that the materials of the respective components may be embrittled by the heat of brazing. Moreover, brazing the rectangular tube body 11 to the top surface of the weld flange 12 results in the addition of the thickness of the flange 12 to the thickness of the bottom of the rectangular tube body 11 which defines the IN and OUT or prominence over the tooth enamel. Consequently, this makes it impossible to adjust the value of IN/OUT H to 0.3 mm according to the orthodontist's requirement. In a typical case where the bottom of the rectangular tube body 11 has a thickness of 0.5 mm and the flange 12 has a thickness of 0.3 mm, the value of H is 0.8 mm.
Under the circumstances, a compact, integrally molded buccal tube of the type shown in FIGS. 4A and 4B has recently been proposed. Since this buccal tube is molded as an integral unit (one-piece unit), it has the major advantage of eliminating the cumbersome assembling operation. In addition, it has the advantage of providing great latitude in meeting the orthodontist's requirement for H=0.3 mm. On the other hand, the width of the weld flange 12 in an occluso-gingival direction is adapted to be the same as the width of the rectangular tube body 11 in the same direction and this presents a serious problem when the flange 12 is welded to the band.
FIG. 5 shows how the buccal tube is welded to the band 14. A pair of electrodes 15 in a spot welding machine are used to fix the weld flange 12 to the buccal surface of the band 14. Needless to say, great difficulty is encountered with the welding procedure if the weld flange 12 is narrow. Particularly, due to the pressure applied during electric heating, the weld flange 12 fuses to become disfigured, and as shown in FIG. 6, pressure marks 16 are formed as concave portions and dusts 17 flown due to welding accidentally clog the entrance (exit) of the through-hole 11a, potentially making it impossible for an end of the arch wire to be passed through the hole 11a in the rectangular tube body 11.
A method that could solve the aforementioned problem with the buccal tube of an integral molding type (so-called as a one-piece type) is to increase the length of the weld flange 12 as much as possible in a mesiodistal direction. If the weld flange 12 is elongated in a mesiodistal direction, because this flange 12 curves toward the lingual side, it can be welded in positions far from the entrance and exit of the through-hole 11a in the rectangular tube body 11, thus eliminating the possibility of the disfigured flange or pressure marks to clog the entrance and exit of the through-hole 11a.
This method is effective in preventing the clogging of the entrance and exit of the through-hole 11a. However, if the weld flange 12 is unduly long, the buccal tube no longer conforms to the shape of the band 14. Finally, the band 14 may be deformed upon welding and eventually fails to fit to the crowns of corresponding molars.
A second method that could be applied is to broaden the rectangular tube body 11 as well as the weld flange 12 in an occluso-gingival direction. Given the same size of the through-hole 11a, the rectangular tube body 11 that is broadened together with the weld flange 12 also allows for the weld flange 12 to be welded in such positions that do not interfere with the entrance or exit of the through-hole 11a.
The second method is also free from the problem of blocking the entrance and exit of the through-hole 11a. However, if the rectangular tube body 11 is broadened together with the weld flange 12, it may then have occlusive interference with antagonistic teeth on the occlusion side or it may contact the gingiva on the gingival side to cause its potential swelling. As a further problem, brushing is difficult to perform and this is not desirable to oral hygiene. In addition, the usual practice in the second method is to make the top side (buccal side) of the rectangular tube body 11 round enough to relieve the discomfort that may be felt by the patient after being equipped with the buccal tube. However, the mold to make the rectangular tube body 11 is of such a construction that the position in which the hook 13 is formed lowers in a direction toward the buccal side to increase the chance of the hook 13 of contacting or burying in the gingiva. Further, food debris remaining under the hook 13 is difficult to brush off, again causing a problem in oral hygiene.